156-W Average power, high repetition rate, nanosecond pulse from a large-mode area fiber amplifier

A master-oscillator fiber power amplifier system with a 4.5-m-long Yb 3+ -doped homemade large-mode-area double-clad fiber is reported. Up to 156 W average power of 1064 nm amplified pulse, corresponding to a slope efficiency of 64.9%, has been demonstrated. The amplified pulse possesses a pulse duration of 24 ns and a repetition rate of 50 kHz and demonstrates a good beam quality (M= x 2 .81 and M y 2 =2.66), although no special transverse-mode-controlling techniques were adopted.